1------------------------------------------------------------------------------
2 T H E /proc F I L E S Y S T E M
3------------------------------------------------------------------------------
4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
6 72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9------------------------------------------------------------------------------
10Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12------------------------------------------------------------------------------
13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
14 15Table of Contents
16-----------------
17 18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
21 22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
32 33 2 Modifying System Parameters
34 35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45 46 4 Configuring procfs
47 4.1 Mount options
48 49------------------------------------------------------------------------------
50Preface
51------------------------------------------------------------------------------
52 530.1 Introduction/Credits
54------------------------
55 56This documentation is part of a soon (or so we hope) to be released book on
57the SuSE Linux distribution. As there is no complete documentation for the
58/proc file system and we've used many freely available sources to write these
59chapters, it seems only fair to give the work back to the Linux community.
60This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
61afraid it's still far from complete, but we hope it will be useful. As far as
62we know, it is the first 'all-in-one' document about the /proc file system. It
63is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
64SPARC, AXP, etc., features, you probably won't find what you are looking for.
65It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
66additions and patches are welcome and will be added to this document if you
67mail them to Bodo.
68 69We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
70other people for help compiling this documentation. We'd also like to extend a
71special thank you to Andi Kleen for documentation, which we relied on heavily
72to create this document, as well as the additional information he provided.
73Thanks to everybody else who contributed source or docs to the Linux kernel
74and helped create a great piece of software... :)
75 76If you have any comments, corrections or additions, please don't hesitate to
77contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
78document.
79 80The latest version of this document is available online at
81http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 82 83If the above direction does not works for you, you could try the kernel
84mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
85comandante@zaralinux.com.
86 870.2 Legal Stuff
88---------------
89 90We don't guarantee the correctness of this document, and if you come to us
91complaining about how you screwed up your system because of incorrect
92documentation, we won't feel responsible...
93 94------------------------------------------------------------------------------
95CHAPTER 1: COLLECTING SYSTEM INFORMATION
96------------------------------------------------------------------------------
97 98------------------------------------------------------------------------------
99In This Chapter
100------------------------------------------------------------------------------
101* Investigating the properties of the pseudo file system /proc and its
102 ability to provide information on the running Linux system
103* Examining /proc's structure
104* Uncovering various information about the kernel and the processes running
105 on the system
106------------------------------------------------------------------------------
107 108 109The proc file system acts as an interface to internal data structures in the
110kernel. It can be used to obtain information about the system and to change
111certain kernel parameters at runtime (sysctl).
112 113First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
114show you how you can use /proc/sys to change settings.
115 1161.1 Process-Specific Subdirectories
117-----------------------------------
118 119The directory /proc contains (among other things) one subdirectory for each
120process running on the system, which is named after the process ID (PID).
121 122The link self points to the process reading the file system. Each process
123subdirectory has the entries listed in Table 1-1.
124 125 126Table 1-1: Process specific entries in /proc
127..............................................................................
128 File Content
129 clear_refs Clears page referenced bits shown in smaps output
130 cmdline Command line arguments
131 cpu Current and last cpu in which it was executed (2.4)(smp)
132 cwd Link to the current working directory
133 environ Values of environment variables
134 exe Link to the executable of this process
135 fd Directory, which contains all file descriptors
136 maps Memory maps to executables and library files (2.4)
137 mem Memory held by this process
138 root Link to the root directory of this process
139 stat Process status
140 statm Process memory status information
141 status Process status in human readable form
142 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
143 pagemap Page table
144 stack Report full stack trace, enable via CONFIG_STACKTRACE
145 smaps a extension based on maps, showing the memory consumption of
146 each mapping and flags associated with it
147..............................................................................
148 149For example, to get the status information of a process, all you have to do is
150read the file /proc/PID/status:
151 152 >cat /proc/self/status
153 Name: cat
154 State: R (running)
155 Tgid: 5452
156 Pid: 5452
157 PPid: 743
158 TracerPid: 0 (2.4)
159 Uid: 501 501 501 501
160 Gid: 100 100 100 100
161 FDSize: 256
162 Groups: 100 14 16
163 VmPeak: 5004 kB
164 VmSize: 5004 kB
165 VmLck: 0 kB
166 VmHWM: 476 kB
167 VmRSS: 476 kB
168 VmData: 156 kB
169 VmStk: 88 kB
170 VmExe: 68 kB
171 VmLib: 1412 kB
172 VmPTE: 20 kb
173 VmSwap: 0 kB
174 Threads: 1
175 SigQ: 0/28578
176 SigPnd: 0000000000000000
177 ShdPnd: 0000000000000000
178 SigBlk: 0000000000000000
179 SigIgn: 0000000000000000
180 SigCgt: 0000000000000000
181 CapInh: 00000000fffffeff
182 CapPrm: 0000000000000000
183 CapEff: 0000000000000000
184 CapBnd: ffffffffffffffff
185 Seccomp: 0
186 voluntary_ctxt_switches: 0
187 nonvoluntary_ctxt_switches: 1
188 189This shows you nearly the same information you would get if you viewed it with
190the ps command. In fact, ps uses the proc file system to obtain its
191information. But you get a more detailed view of the process by reading the
192file /proc/PID/status. It fields are described in table 1-2.
193 194The statm file contains more detailed information about the process
195memory usage. Its seven fields are explained in Table 1-3. The stat file
196contains details information about the process itself. Its fields are
197explained in Table 1-4.
198 199(for SMP CONFIG users)
200For making accounting scalable, RSS related information are handled in
201asynchronous manner and the vaule may not be very precise. To see a precise
202snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
203It's slow but very precise.
204 205Table 1-2: Contents of the status files (as of 2.6.30-rc7)
206..............................................................................
207 Field Content
208 Name filename of the executable
209 State state (R is running, S is sleeping, D is sleeping
210 in an uninterruptible wait, Z is zombie,
211 T is traced or stopped)
212 Tgid thread group ID
213 Pid process id
214 PPid process id of the parent process
215 TracerPid PID of process tracing this process (0 if not)
216 Uid Real, effective, saved set, and file system UIDs
217 Gid Real, effective, saved set, and file system GIDs
218 FDSize number of file descriptor slots currently allocated
219 Groups supplementary group list
220 VmPeak peak virtual memory size
221 VmSize total program size
222 VmLck locked memory size
223 VmHWM peak resident set size ("high water mark")
224 VmRSS size of memory portions
225 VmData size of data, stack, and text segments
226 VmStk size of data, stack, and text segments
227 VmExe size of text segment
228 VmLib size of shared library code
229 VmPTE size of page table entries
230 VmSwap size of swap usage (the number of referred swapents)
231 Threads number of threads
232 SigQ number of signals queued/max. number for queue
233 SigPnd bitmap of pending signals for the thread
234 ShdPnd bitmap of shared pending signals for the process
235 SigBlk bitmap of blocked signals
236 SigIgn bitmap of ignored signals
237 SigCgt bitmap of catched signals
238 CapInh bitmap of inheritable capabilities
239 CapPrm bitmap of permitted capabilities
240 CapEff bitmap of effective capabilities
241 CapBnd bitmap of capabilities bounding set
242 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
243 Cpus_allowed mask of CPUs on which this process may run
244 Cpus_allowed_list Same as previous, but in "list format"
245 Mems_allowed mask of memory nodes allowed to this process
246 Mems_allowed_list Same as previous, but in "list format"
247 voluntary_ctxt_switches number of voluntary context switches
248 nonvoluntary_ctxt_switches number of non voluntary context switches
249..............................................................................
250 251Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
252..............................................................................
253 Field Content
254 size total program size (pages) (same as VmSize in status)
255 resident size of memory portions (pages) (same as VmRSS in status)
256 shared number of pages that are shared (i.e. backed by a file)
257 trs number of pages that are 'code' (not including libs; broken,
258 includes data segment)
259 lrs number of pages of library (always 0 on 2.6)
260 drs number of pages of data/stack (including libs; broken,
261 includes library text)
262 dt number of dirty pages (always 0 on 2.6)
263..............................................................................
264 265 266Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
267..............................................................................
268 Field Content
269 pid process id
270 tcomm filename of the executable
271 state state (R is running, S is sleeping, D is sleeping in an
272 uninterruptible wait, Z is zombie, T is traced or stopped)
273 ppid process id of the parent process
274 pgrp pgrp of the process
275 sid session id
276 tty_nr tty the process uses
277 tty_pgrp pgrp of the tty
278 flags task flags
279 min_flt number of minor faults
280 cmin_flt number of minor faults with child's
281 maj_flt number of major faults
282 cmaj_flt number of major faults with child's
283 utime user mode jiffies
284 stime kernel mode jiffies
285 cutime user mode jiffies with child's
286 cstime kernel mode jiffies with child's
287 priority priority level
288 nice nice level
289 num_threads number of threads
290 it_real_value (obsolete, always 0)
291 start_time time the process started after system boot
292 vsize virtual memory size
293 rss resident set memory size
294 rsslim current limit in bytes on the rss
295 start_code address above which program text can run
296 end_code address below which program text can run
297 start_stack address of the start of the main process stack
298 esp current value of ESP
299 eip current value of EIP
300 pending bitmap of pending signals
301 blocked bitmap of blocked signals
302 sigign bitmap of ignored signals
303 sigcatch bitmap of catched signals
304 wchan address where process went to sleep
305 0 (place holder)
306 0 (place holder)
307 exit_signal signal to send to parent thread on exit
308 task_cpu which CPU the task is scheduled on
309 rt_priority realtime priority
310 policy scheduling policy (man sched_setscheduler)
311 blkio_ticks time spent waiting for block IO
312 gtime guest time of the task in jiffies
313 cgtime guest time of the task children in jiffies
314 start_data address above which program data+bss is placed
315 end_data address below which program data+bss is placed
316 start_brk address above which program heap can be expanded with brk()
317 arg_start address above which program command line is placed
318 arg_end address below which program command line is placed
319 env_start address above which program environment is placed
320 env_end address below which program environment is placed
321 exit_code the thread's exit_code in the form reported by the waitpid system call
322..............................................................................
323 324The /proc/PID/maps file containing the currently mapped memory regions and
325their access permissions.
326 327The format is:
328 329address perms offset dev inode pathname
330 33108048000-08049000 r-xp 00000000 03:00 8312 /opt/test
33208049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3330804a000-0806b000 rw-p 00000000 00:00 0 [heap]
334a7cb1000-a7cb2000 ---p 00000000 00:00 0
335a7cb2000-a7eb2000 rw-p 00000000 00:00 0
336a7eb2000-a7eb3000 ---p 00000000 00:00 0
337a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001]
338a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
339a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
340a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
341a800b000-a800e000 rw-p 00000000 00:00 0
342a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
343a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
344a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
345a8024000-a8027000 rw-p 00000000 00:00 0
346a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
347a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
348a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
349aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
350ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
351 352where "address" is the address space in the process that it occupies, "perms"
353is a set of permissions:
354 355 r = read
356 w = write
357 x = execute
358 s = shared
359 p = private (copy on write)
360 361"offset" is the offset into the mapping, "dev" is the device (major:minor), and
362"inode" is the inode on that device. 0 indicates that no inode is associated
363with the memory region, as the case would be with BSS (uninitialized data).
364The "pathname" shows the name associated file for this mapping. If the mapping
365is not associated with a file:
366 367 [heap] = the heap of the program
368 [stack] = the stack of the main process
369 [stack:1001] = the stack of the thread with tid 1001
370 [vdso] = the "virtual dynamic shared object",
371 the kernel system call handler
372 373 or if empty, the mapping is anonymous.
374 375The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
376of the individual tasks of a process. In this file you will see a mapping marked
377as [stack] if that task sees it as a stack. This is a key difference from the
378content of /proc/PID/maps, where you will see all mappings that are being used
379as stack by all of those tasks. Hence, for the example above, the task-level
380map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
381 38208048000-08049000 r-xp 00000000 03:00 8312 /opt/test
38308049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3840804a000-0806b000 rw-p 00000000 00:00 0 [heap]
385a7cb1000-a7cb2000 ---p 00000000 00:00 0
386a7cb2000-a7eb2000 rw-p 00000000 00:00 0
387a7eb2000-a7eb3000 ---p 00000000 00:00 0
388a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack]
389a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
390a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
391a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
392a800b000-a800e000 rw-p 00000000 00:00 0
393a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
394a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
395a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
396a8024000-a8027000 rw-p 00000000 00:00 0
397a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
398a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
399a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
400aff35000-aff4a000 rw-p 00000000 00:00 0
401ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
402 403The /proc/PID/smaps is an extension based on maps, showing the memory
404consumption for each of the process's mappings. For each of mappings there
405is a series of lines such as the following:
406 40708048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
408Size: 1084 kB
409Rss: 892 kB
410Pss: 374 kB
411Shared_Clean: 892 kB
412Shared_Dirty: 0 kB
413Private_Clean: 0 kB
414Private_Dirty: 0 kB
415Referenced: 892 kB
416Anonymous: 0 kB
417Swap: 0 kB
418KernelPageSize: 4 kB
419MMUPageSize: 4 kB
420Locked: 374 kB
421VmFlags: rd ex mr mw me de
422 423the first of these lines shows the same information as is displayed for the
424mapping in /proc/PID/maps. The remaining lines show the size of the mapping
425(size), the amount of the mapping that is currently resident in RAM (RSS), the
426process' proportional share of this mapping (PSS), the number of clean and
427dirty private pages in the mapping. Note that even a page which is part of a
428MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used
429by only one process, is accounted as private and not as shared. "Referenced"
430indicates the amount of memory currently marked as referenced or accessed.
431"Anonymous" shows the amount of memory that does not belong to any file. Even
432a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
433and a page is modified, the file page is replaced by a private anonymous copy.
434"Swap" shows how much would-be-anonymous memory is also used, but out on
435swap.
436 437"VmFlags" field deserves a separate description. This member represents the kernel
438flags associated with the particular virtual memory area in two letter encoded
439manner. The codes are the following:
440 rd - readable
441 wr - writeable
442 ex - executable
443 sh - shared
444 mr - may read
445 mw - may write
446 me - may execute
447 ms - may share
448 gd - stack segment growns down
449 pf - pure PFN range
450 dw - disabled write to the mapped file
451 lo - pages are locked in memory
452 io - memory mapped I/O area
453 sr - sequential read advise provided
454 rr - random read advise provided
455 dc - do not copy area on fork
456 de - do not expand area on remapping
457 ac - area is accountable
458 nr - swap space is not reserved for the area
459 ht - area uses huge tlb pages
460 nl - non-linear mapping
461 ar - architecture specific flag
462 dd - do not include area into core dump
463 mm - mixed map area
464 hg - huge page advise flag
465 nh - no-huge page advise flag
466 mg - mergable advise flag
467 468Note that there is no guarantee that every flag and associated mnemonic will
469be present in all further kernel releases. Things get changed, the flags may
470be vanished or the reverse -- new added.
471 472This file is only present if the CONFIG_MMU kernel configuration option is
473enabled.
474 475The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
476bits on both physical and virtual pages associated with a process, and the
477soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
478To clear the bits for all the pages associated with the process
479 > echo 1 > /proc/PID/clear_refs
480 481To clear the bits for the anonymous pages associated with the process
482 > echo 2 > /proc/PID/clear_refs
483 484To clear the bits for the file mapped pages associated with the process
485 > echo 3 > /proc/PID/clear_refs
486 487To clear the soft-dirty bit
488 > echo 4 > /proc/PID/clear_refs
489 490Any other value written to /proc/PID/clear_refs will have no effect.
491 492The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
493using /proc/kpageflags and number of times a page is mapped using
494/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
495 4961.2 Kernel data
497---------------
498 499Similar to the process entries, the kernel data files give information about
500the running kernel. The files used to obtain this information are contained in
501/proc and are listed in Table 1-5. Not all of these will be present in your
502system. It depends on the kernel configuration and the loaded modules, which
503files are there, and which are missing.
504 505Table 1-5: Kernel info in /proc
506..............................................................................
507 File Content
508 apm Advanced power management info
509 buddyinfo Kernel memory allocator information (see text) (2.5)
510 bus Directory containing bus specific information
511 cmdline Kernel command line
512 cpuinfo Info about the CPU
513 devices Available devices (block and character)
514 dma Used DMS channels
515 filesystems Supported filesystems
516 driver Various drivers grouped here, currently rtc (2.4)
517 execdomains Execdomains, related to security (2.4)
518 fb Frame Buffer devices (2.4)
519 fs File system parameters, currently nfs/exports (2.4)
520 ide Directory containing info about the IDE subsystem
521 interrupts Interrupt usage
522 iomem Memory map (2.4)
523 ioports I/O port usage
524 irq Masks for irq to cpu affinity (2.4)(smp?)
525 isapnp ISA PnP (Plug&Play) Info (2.4)
526 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
527 kmsg Kernel messages
528 ksyms Kernel symbol table
529 loadavg Load average of last 1, 5 & 15 minutes
530 locks Kernel locks
531 meminfo Memory info
532 misc Miscellaneous
533 modules List of loaded modules
534 mounts Mounted filesystems
535 net Networking info (see text)
536 pagetypeinfo Additional page allocator information (see text) (2.5)
537 partitions Table of partitions known to the system
538 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
539 decoupled by lspci (2.4)
540 rtc Real time clock
541 scsi SCSI info (see text)
542 slabinfo Slab pool info
543 softirqs softirq usage
544 stat Overall statistics
545 swaps Swap space utilization
546 sys See chapter 2
547 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
548 tty Info of tty drivers
549 uptime System uptime
550 version Kernel version
551 video bttv info of video resources (2.4)
552 vmallocinfo Show vmalloced areas
553..............................................................................
554 555You can, for example, check which interrupts are currently in use and what
556they are used for by looking in the file /proc/interrupts:
557 558 > cat /proc/interrupts
559 CPU0
560 0: 8728810 XT-PIC timer
561 1: 895 XT-PIC keyboard
562 2: 0 XT-PIC cascade
563 3: 531695 XT-PIC aha152x
564 4: 2014133 XT-PIC serial
565 5: 44401 XT-PIC pcnet_cs
566 8: 2 XT-PIC rtc
567 11: 8 XT-PIC i82365
568 12: 182918 XT-PIC PS/2 Mouse
569 13: 1 XT-PIC fpu
570 14: 1232265 XT-PIC ide0
571 15: 7 XT-PIC ide1
572 NMI: 0
573 574In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
575output of a SMP machine):
576 577 > cat /proc/interrupts
578 579 CPU0 CPU1
580 0: 1243498 1214548 IO-APIC-edge timer
581 1: 8949 8958 IO-APIC-edge keyboard
582 2: 0 0 XT-PIC cascade
583 5: 11286 10161 IO-APIC-edge soundblaster
584 8: 1 0 IO-APIC-edge rtc
585 9: 27422 27407 IO-APIC-edge 3c503
586 12: 113645 113873 IO-APIC-edge PS/2 Mouse
587 13: 0 0 XT-PIC fpu
588 14: 22491 24012 IO-APIC-edge ide0
589 15: 2183 2415 IO-APIC-edge ide1
590 17: 30564 30414 IO-APIC-level eth0
591 18: 177 164 IO-APIC-level bttv
592 NMI: 2457961 2457959
593 LOC: 2457882 2457881
594 ERR: 2155
595 596NMI is incremented in this case because every timer interrupt generates a NMI
597(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
598 599LOC is the local interrupt counter of the internal APIC of every CPU.
600 601ERR is incremented in the case of errors in the IO-APIC bus (the bus that
602connects the CPUs in a SMP system. This means that an error has been detected,
603the IO-APIC automatically retry the transmission, so it should not be a big
604problem, but you should read the SMP-FAQ.
605 606In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
607/proc/interrupts to display every IRQ vector in use by the system, not
608just those considered 'most important'. The new vectors are:
609 610 THR -- interrupt raised when a machine check threshold counter
611 (typically counting ECC corrected errors of memory or cache) exceeds
612 a configurable threshold. Only available on some systems.
613 614 TRM -- a thermal event interrupt occurs when a temperature threshold
615 has been exceeded for the CPU. This interrupt may also be generated
616 when the temperature drops back to normal.
617 618 SPU -- a spurious interrupt is some interrupt that was raised then lowered
619 by some IO device before it could be fully processed by the APIC. Hence
620 the APIC sees the interrupt but does not know what device it came from.
621 For this case the APIC will generate the interrupt with a IRQ vector
622 of 0xff. This might also be generated by chipset bugs.
623 624 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
625 sent from one CPU to another per the needs of the OS. Typically,
626 their statistics are used by kernel developers and interested users to
627 determine the occurrence of interrupts of the given type.
628 629The above IRQ vectors are displayed only when relevant. For example,
630the threshold vector does not exist on x86_64 platforms. Others are
631suppressed when the system is a uniprocessor. As of this writing, only
632i386 and x86_64 platforms support the new IRQ vector displays.
633 634Of some interest is the introduction of the /proc/irq directory to 2.4.
635It could be used to set IRQ to CPU affinity, this means that you can "hook" an
636IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
637irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
638prof_cpu_mask.
639 640For example
641 > ls /proc/irq/
642 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
643 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
644 > ls /proc/irq/0/
645 smp_affinity
646 647smp_affinity is a bitmask, in which you can specify which CPUs can handle the
648IRQ, you can set it by doing:
649 650 > echo 1 > /proc/irq/10/smp_affinity
651 652This means that only the first CPU will handle the IRQ, but you can also echo
6535 which means that only the first and fourth CPU can handle the IRQ.
654 655The contents of each smp_affinity file is the same by default:
656 657 > cat /proc/irq/0/smp_affinity
658 ffffffff
659 660There is an alternate interface, smp_affinity_list which allows specifying
661a cpu range instead of a bitmask:
662 663 > cat /proc/irq/0/smp_affinity_list
664 1024-1031
665 666The default_smp_affinity mask applies to all non-active IRQs, which are the
667IRQs which have not yet been allocated/activated, and hence which lack a
668/proc/irq/[0-9]* directory.
669 670The node file on an SMP system shows the node to which the device using the IRQ
671reports itself as being attached. This hardware locality information does not
672include information about any possible driver locality preference.
673 674prof_cpu_mask specifies which CPUs are to be profiled by the system wide
675profiler. Default value is ffffffff (all cpus if there are only 32 of them).
676 677The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
678between all the CPUs which are allowed to handle it. As usual the kernel has
679more info than you and does a better job than you, so the defaults are the
680best choice for almost everyone. [Note this applies only to those IO-APIC's
681that support "Round Robin" interrupt distribution.]
682 683There are three more important subdirectories in /proc: net, scsi, and sys.
684The general rule is that the contents, or even the existence of these
685directories, depend on your kernel configuration. If SCSI is not enabled, the
686directory scsi may not exist. The same is true with the net, which is there
687only when networking support is present in the running kernel.
688 689The slabinfo file gives information about memory usage at the slab level.
690Linux uses slab pools for memory management above page level in version 2.2.
691Commonly used objects have their own slab pool (such as network buffers,
692directory cache, and so on).
693 694..............................................................................
695 696> cat /proc/buddyinfo
697 698Node 0, zone DMA 0 4 5 4 4 3 ...
699Node 0, zone Normal 1 0 0 1 101 8 ...
700Node 0, zone HighMem 2 0 0 1 1 0 ...
701 702External fragmentation is a problem under some workloads, and buddyinfo is a
703useful tool for helping diagnose these problems. Buddyinfo will give you a
704clue as to how big an area you can safely allocate, or why a previous
705allocation failed.
706 707Each column represents the number of pages of a certain order which are
708available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
709ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
710available in ZONE_NORMAL, etc...
711 712More information relevant to external fragmentation can be found in
713pagetypeinfo.
714 715> cat /proc/pagetypeinfo
716Page block order: 9
717Pages per block: 512
718 719Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
720Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
721Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
722Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
723Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
724Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
725Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
726Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
727Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
728Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
729Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
730 731Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
732Node 0, zone DMA 2 0 5 1 0
733Node 0, zone DMA32 41 6 967 2 0
734 735Fragmentation avoidance in the kernel works by grouping pages of different
736migrate types into the same contiguous regions of memory called page blocks.
737A page block is typically the size of the default hugepage size e.g. 2MB on
738X86-64. By keeping pages grouped based on their ability to move, the kernel
739can reclaim pages within a page block to satisfy a high-order allocation.
740 741The pagetypinfo begins with information on the size of a page block. It
742then gives the same type of information as buddyinfo except broken down
743by migrate-type and finishes with details on how many page blocks of each
744type exist.
745 746If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
747from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
748make an estimate of the likely number of huge pages that can be allocated
749at a given point in time. All the "Movable" blocks should be allocatable
750unless memory has been mlock()'d. Some of the Reclaimable blocks should
751also be allocatable although a lot of filesystem metadata may have to be
752reclaimed to achieve this.
753 754..............................................................................
755 756meminfo:
757 758Provides information about distribution and utilization of memory. This
759varies by architecture and compile options. The following is from a
76016GB PIII, which has highmem enabled. You may not have all of these fields.
761 762> cat /proc/meminfo
763 764The "Locked" indicates whether the mapping is locked in memory or not.
765 766 767MemTotal: 16344972 kB
768MemFree: 13634064 kB
769Buffers: 3656 kB
770Cached: 1195708 kB
771SwapCached: 0 kB
772Active: 891636 kB
773Inactive: 1077224 kB
774HighTotal: 15597528 kB
775HighFree: 13629632 kB
776LowTotal: 747444 kB
777LowFree: 4432 kB
778SwapTotal: 0 kB
779SwapFree: 0 kB
780Dirty: 968 kB
781Writeback: 0 kB
782AnonPages: 861800 kB
783Mapped: 280372 kB
784Slab: 284364 kB
785SReclaimable: 159856 kB
786SUnreclaim: 124508 kB
787PageTables: 24448 kB
788NFS_Unstable: 0 kB
789Bounce: 0 kB
790WritebackTmp: 0 kB
791CommitLimit: 7669796 kB
792Committed_AS: 100056 kB
793VmallocTotal: 112216 kB
794VmallocUsed: 428 kB
795VmallocChunk: 111088 kB
796AnonHugePages: 49152 kB
797 798 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
799 bits and the kernel binary code)
800 MemFree: The sum of LowFree+HighFree
801 Buffers: Relatively temporary storage for raw disk blocks
802 shouldn't get tremendously large (20MB or so)
803 Cached: in-memory cache for files read from the disk (the
804 pagecache). Doesn't include SwapCached
805 SwapCached: Memory that once was swapped out, is swapped back in but
806 still also is in the swapfile (if memory is needed it
807 doesn't need to be swapped out AGAIN because it is already
808 in the swapfile. This saves I/O)
809 Active: Memory that has been used more recently and usually not
810 reclaimed unless absolutely necessary.
811 Inactive: Memory which has been less recently used. It is more
812 eligible to be reclaimed for other purposes
813 HighTotal:
814 HighFree: Highmem is all memory above ~860MB of physical memory
815 Highmem areas are for use by userspace programs, or
816 for the pagecache. The kernel must use tricks to access
817 this memory, making it slower to access than lowmem.
818 LowTotal:
819 LowFree: Lowmem is memory which can be used for everything that
820 highmem can be used for, but it is also available for the
821 kernel's use for its own data structures. Among many
822 other things, it is where everything from the Slab is
823 allocated. Bad things happen when you're out of lowmem.
824 SwapTotal: total amount of swap space available
825 SwapFree: Memory which has been evicted from RAM, and is temporarily
826 on the disk
827 Dirty: Memory which is waiting to get written back to the disk
828 Writeback: Memory which is actively being written back to the disk
829 AnonPages: Non-file backed pages mapped into userspace page tables
830AnonHugePages: Non-file backed huge pages mapped into userspace page tables
831 Mapped: files which have been mmaped, such as libraries
832 Slab: in-kernel data structures cache
833SReclaimable: Part of Slab, that might be reclaimed, such as caches
834 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
835 PageTables: amount of memory dedicated to the lowest level of page
836 tables.
837NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
838 storage
839 Bounce: Memory used for block device "bounce buffers"
840WritebackTmp: Memory used by FUSE for temporary writeback buffers
841 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
842 this is the total amount of memory currently available to
843 be allocated on the system. This limit is only adhered to
844 if strict overcommit accounting is enabled (mode 2 in
845 'vm.overcommit_memory').
846 The CommitLimit is calculated with the following formula:
847 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
848 For example, on a system with 1G of physical RAM and 7G
849 of swap with a `vm.overcommit_ratio` of 30 it would
850 yield a CommitLimit of 7.3G.
851 For more details, see the memory overcommit documentation
852 in vm/overcommit-accounting.
853Committed_AS: The amount of memory presently allocated on the system.
854 The committed memory is a sum of all of the memory which
855 has been allocated by processes, even if it has not been
856 "used" by them as of yet. A process which malloc()'s 1G
857 of memory, but only touches 300M of it will only show up
858 as using 300M of memory even if it has the address space
859 allocated for the entire 1G. This 1G is memory which has
860 been "committed" to by the VM and can be used at any time
861 by the allocating application. With strict overcommit
862 enabled on the system (mode 2 in 'vm.overcommit_memory'),
863 allocations which would exceed the CommitLimit (detailed
864 above) will not be permitted. This is useful if one needs
865 to guarantee that processes will not fail due to lack of
866 memory once that memory has been successfully allocated.
867VmallocTotal: total size of vmalloc memory area
868 VmallocUsed: amount of vmalloc area which is used
869VmallocChunk: largest contiguous block of vmalloc area which is free
870 871..............................................................................
872 873vmallocinfo:
874 875Provides information about vmalloced/vmaped areas. One line per area,
876containing the virtual address range of the area, size in bytes,
877caller information of the creator, and optional information depending
878on the kind of area :
879 880 pages=nr number of pages
881 phys=addr if a physical address was specified
882 ioremap I/O mapping (ioremap() and friends)
883 vmalloc vmalloc() area
884 vmap vmap()ed pages
885 user VM_USERMAP area
886 vpages buffer for pages pointers was vmalloced (huge area)
887 N<node>=nr (Only on NUMA kernels)
888 Number of pages allocated on memory node <node>
889 890> cat /proc/vmallocinfo
8910xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
892 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
8930xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
894 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
8950xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
896 phys=7fee8000 ioremap
8970xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
898 phys=7fee7000 ioremap
8990xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
9000xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
901 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
9020xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
903 pages=2 vmalloc N1=2
9040xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
905 /0x130 [x_tables] pages=4 vmalloc N0=4
9060xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
907 pages=14 vmalloc N2=14
9080xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
909 pages=4 vmalloc N1=4
9100xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
911 pages=2 vmalloc N1=2
9120xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
913 pages=10 vmalloc N0=10
914 915..............................................................................
916 917softirqs:
918 919Provides counts of softirq handlers serviced since boot time, for each cpu.
920 921> cat /proc/softirqs
922 CPU0 CPU1 CPU2 CPU3
923 HI: 0 0 0 0
924 TIMER: 27166 27120 27097 27034
925 NET_TX: 0 0 0 17
926 NET_RX: 42 0 0 39
927 BLOCK: 0 0 107 1121
928 TASKLET: 0 0 0 290
929 SCHED: 27035 26983 26971 26746
930 HRTIMER: 0 0 0 0
931 RCU: 1678 1769 2178 2250
932 933 9341.3 IDE devices in /proc/ide
935----------------------------
936 937The subdirectory /proc/ide contains information about all IDE devices of which
938the kernel is aware. There is one subdirectory for each IDE controller, the
939file drivers and a link for each IDE device, pointing to the device directory
940in the controller specific subtree.
941 942The file drivers contains general information about the drivers used for the
943IDE devices:
944 945 > cat /proc/ide/drivers
946 ide-cdrom version 4.53
947 ide-disk version 1.08
948 949More detailed information can be found in the controller specific
950subdirectories. These are named ide0, ide1 and so on. Each of these
951directories contains the files shown in table 1-6.
952 953 954Table 1-6: IDE controller info in /proc/ide/ide?
955..............................................................................
956 File Content
957 channel IDE channel (0 or 1)
958 config Configuration (only for PCI/IDE bridge)
959 mate Mate name
960 model Type/Chipset of IDE controller
961..............................................................................
962 963Each device connected to a controller has a separate subdirectory in the
964controllers directory. The files listed in table 1-7 are contained in these
965directories.
966 967 968Table 1-7: IDE device information
969..............................................................................
970 File Content
971 cache The cache
972 capacity Capacity of the medium (in 512Byte blocks)
973 driver driver and version
974 geometry physical and logical geometry
975 identify device identify block
976 media media type
977 model device identifier
978 settings device setup
979 smart_thresholds IDE disk management thresholds
980 smart_values IDE disk management values
981..............................................................................
982 983The most interesting file is settings. This file contains a nice overview of
984the drive parameters:
985 986 # cat /proc/ide/ide0/hda/settings
987 name value min max mode
988 ---- ----- --- --- ----
989 bios_cyl 526 0 65535 rw
990 bios_head 255 0 255 rw
991 bios_sect 63 0 63 rw
992 breada_readahead 4 0 127 rw
993 bswap 0 0 1 r
994 file_readahead 72 0 2097151 rw
995 io_32bit 0 0 3 rw
996 keepsettings 0 0 1 rw
997 max_kb_per_request 122 1 127 rw
998 multcount 0 0 8 rw
999 nice1 1 0 1 rw
1000 nowerr 0 0 1 rw

1001 pio_mode write-only 0 255 w
1002 slow 0 0 1 rw
1003 unmaskirq 0 0 1 rw
1004 using_dma 0 0 1 rw
1005100610071.4 Networking info in /proc/net
1008--------------------------------
10091010The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1011additional values you get for IP version 6 if you configure the kernel to
1012support this. Table 1-9 lists the files and their meaning.
101310141015Table 1-8: IPv6 info in /proc/net
1016..............................................................................
1017 File Content
1018 udp6 UDP sockets (IPv6)
1019 tcp6 TCP sockets (IPv6)
1020 raw6 Raw device statistics (IPv6)
1021 igmp6 IP multicast addresses, which this host joined (IPv6)
1022 if_inet6 List of IPv6 interface addresses
1023 ipv6_route Kernel routing table for IPv6
1024 rt6_stats Global IPv6 routing tables statistics
1025 sockstat6 Socket statistics (IPv6)
1026 snmp6 Snmp data (IPv6)
1027..............................................................................
102810291030Table 1-9: Network info in /proc/net
1031..............................................................................
1032 File Content
1033 arp Kernel ARP table
1034 dev network devices with statistics
1035 dev_mcast the Layer2 multicast groups a device is listening too
1036 (interface index, label, number of references, number of bound
1037 addresses).
1038 dev_stat network device status
1039 ip_fwchains Firewall chain linkage
1040 ip_fwnames Firewall chain names
1041 ip_masq Directory containing the masquerading tables
1042 ip_masquerade Major masquerading table
1043 netstat Network statistics
1044 raw raw device statistics
1045 route Kernel routing table
1046 rpc Directory containing rpc info
1047 rt_cache Routing cache
1048 snmp SNMP data
1049 sockstat Socket statistics
1050 tcp TCP sockets
1051 udp UDP sockets
1052 unix UNIX domain sockets
1053 wireless Wireless interface data (Wavelan etc)
1054 igmp IP multicast addresses, which this host joined
1055 psched Global packet scheduler parameters.
1056 netlink List of PF_NETLINK sockets
1057 ip_mr_vifs List of multicast virtual interfaces
1058 ip_mr_cache List of multicast routing cache
1059..............................................................................
10601061You can use this information to see which network devices are available in
1062your system and how much traffic was routed over those devices:
10631064 > cat /proc/net/dev
1065 Inter-|Receive |[...
1066 face |bytes packets errs drop fifo frame compressed multicast|[...
1067 lo: 908188 5596 0 0 0 0 0 0 [...
1068 ppp0:15475140 20721 410 0 0 410 0 0 [...
1069 eth0: 614530 7085 0 0 0 0 0 1 [...
10701071 ...] Transmit
1072 ...] bytes packets errs drop fifo colls carrier compressed
1073 ...] 908188 5596 0 0 0 0 0 0
1074 ...] 1375103 17405 0 0 0 0 0 0
1075 ...] 1703981 5535 0 0 0 3 0 0
10761077In addition, each Channel Bond interface has its own directory. For
1078example, the bond0 device will have a directory called /proc/net/bond0/.
1079It will contain information that is specific to that bond, such as the
1080current slaves of the bond, the link status of the slaves, and how
1081many times the slaves link has failed.
108210831.5 SCSI info
1084-------------
10851086If you have a SCSI host adapter in your system, you'll find a subdirectory
1087named after the driver for this adapter in /proc/scsi. You'll also see a list
1088of all recognized SCSI devices in /proc/scsi:
10891090 >cat /proc/scsi/scsi
1091 Attached devices:
1092 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1093 Vendor: IBM Model: DGHS09U Rev: 03E0
1094 Type: Direct-Access ANSI SCSI revision: 03
1095 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1096 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1097 Type: CD-ROM ANSI SCSI revision: 02
109810991100The directory named after the driver has one file for each adapter found in
1101the system. These files contain information about the controller, including
1102the used IRQ and the IO address range. The amount of information shown is
1103dependent on the adapter you use. The example shows the output for an Adaptec
1104AHA-2940 SCSI adapter:
11051106 > cat /proc/scsi/aic7xxx/0
11071108 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1109 Compile Options:
1110 TCQ Enabled By Default : Disabled
1111 AIC7XXX_PROC_STATS : Disabled
1112 AIC7XXX_RESET_DELAY : 5
1113 Adapter Configuration:
1114 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1115 Ultra Wide Controller
1116 PCI MMAPed I/O Base: 0xeb001000
1117 Adapter SEEPROM Config: SEEPROM found and used.
1118 Adaptec SCSI BIOS: Enabled
1119 IRQ: 10
1120 SCBs: Active 0, Max Active 2,
1121 Allocated 15, HW 16, Page 255
1122 Interrupts: 160328
1123 BIOS Control Word: 0x18b6
1124 Adapter Control Word: 0x005b
1125 Extended Translation: Enabled
1126 Disconnect Enable Flags: 0xffff
1127 Ultra Enable Flags: 0x0001
1128 Tag Queue Enable Flags: 0x0000
1129 Ordered Queue Tag Flags: 0x0000
1130 Default Tag Queue Depth: 8
1131 Tagged Queue By Device array for aic7xxx host instance 0:
1132 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1133 Actual queue depth per device for aic7xxx host instance 0:
1134 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1135 Statistics:
1136 (scsi0:0:0:0)
1137 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1138 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1139 Total transfers 160151 (74577 reads and 85574 writes)
1140 (scsi0:0:6:0)
1141 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1142 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1143 Total transfers 0 (0 reads and 0 writes)
1144114511461.6 Parallel port info in /proc/parport
1147---------------------------------------
11481149The directory /proc/parport contains information about the parallel ports of
1150your system. It has one subdirectory for each port, named after the port
1151number (0,1,2,...).
11521153These directories contain the four files shown in Table 1-10.
115411551156Table 1-10: Files in /proc/parport
1157..............................................................................
1158 File Content
1159 autoprobe Any IEEE-1284 device ID information that has been acquired.
1160 devices list of the device drivers using that port. A + will appear by the
1161 name of the device currently using the port (it might not appear
1162 against any).
1163 hardware Parallel port's base address, IRQ line and DMA channel.
1164 irq IRQ that parport is using for that port. This is in a separate
1165 file to allow you to alter it by writing a new value in (IRQ
1166 number or none).
1167..............................................................................
116811691.7 TTY info in /proc/tty
1170-------------------------
11711172Information about the available and actually used tty's can be found in the
1173directory /proc/tty.You'll find entries for drivers and line disciplines in
1174this directory, as shown in Table 1-11.
117511761177Table 1-11: Files in /proc/tty
1178..............................................................................
1179 File Content
1180 drivers list of drivers and their usage
1181 ldiscs registered line disciplines
1182 driver/serial usage statistic and status of single tty lines
1183..............................................................................
11841185To see which tty's are currently in use, you can simply look into the file
1186/proc/tty/drivers:
11871188 > cat /proc/tty/drivers
1189 pty_slave /dev/pts 136 0-255 pty:slave
1190 pty_master /dev/ptm 128 0-255 pty:master
1191 pty_slave /dev/ttyp 3 0-255 pty:slave
1192 pty_master /dev/pty 2 0-255 pty:master
1193 serial /dev/cua 5 64-67 serial:callout
1194 serial /dev/ttyS 4 64-67 serial
1195 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1196 /dev/ptmx /dev/ptmx 5 2 system
1197 /dev/console /dev/console 5 1 system:console
1198 /dev/tty /dev/tty 5 0 system:/dev/tty
1199 unknown /dev/tty 4 1-63 console
1200120112021.8 Miscellaneous kernel statistics in /proc/stat
1203-------------------------------------------------
12041205Various pieces of information about kernel activity are available in the
1206/proc/stat file. All of the numbers reported in this file are aggregates
1207since the system first booted. For a quick look, simply cat the file:
12081209 > cat /proc/stat
1210 cpu 2255 34 2290 22625563 6290 127 456 0 0
1211 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1212 cpu1 1123 0 849 11313845 2614 0 18 0 0
1213 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1214 ctxt 1990473
1215 btime 1062191376
1216 processes 2915
1217 procs_running 1
1218 procs_blocked 0
1219 softirq 183433 0 21755 12 39 1137 231 21459 2263
12201221The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1222lines. These numbers identify the amount of time the CPU has spent performing
1223different kinds of work. Time units are in USER_HZ (typically hundredths of a
1224second). The meanings of the columns are as follows, from left to right:
12251226- user: normal processes executing in user mode
1227- nice: niced processes executing in user mode
1228- system: processes executing in kernel mode
1229- idle: twiddling thumbs
1230- iowait: waiting for I/O to complete
1231- irq: servicing interrupts
1232- softirq: servicing softirqs
1233- steal: involuntary wait
1234- guest: running a normal guest
1235- guest_nice: running a niced guest
12361237The "intr" line gives counts of interrupts serviced since boot time, for each
1238of the possible system interrupts. The first column is the total of all
1239interrupts serviced; each subsequent column is the total for that particular
1240interrupt.
12411242The "ctxt" line gives the total number of context switches across all CPUs.
12431244The "btime" line gives the time at which the system booted, in seconds since
1245the Unix epoch.
12461247The "processes" line gives the number of processes and threads created, which
1248includes (but is not limited to) those created by calls to the fork() and
1249clone() system calls.
12501251The "procs_running" line gives the total number of threads that are
1252running or ready to run (i.e., the total number of runnable threads).
12531254The "procs_blocked" line gives the number of processes currently blocked,
1255waiting for I/O to complete.
12561257The "softirq" line gives counts of softirqs serviced since boot time, for each
1258of the possible system softirqs. The first column is the total of all
1259softirqs serviced; each subsequent column is the total for that particular
1260softirq.
1261126212631.9 Ext4 file system parameters
1264------------------------------
12651266Information about mounted ext4 file systems can be found in
1267/proc/fs/ext4. Each mounted filesystem will have a directory in
1268/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1269/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1270in Table 1-12, below.
12711272Table 1-12: Files in /proc/fs/ext4/<devname>
1273..............................................................................
1274 File Content
1275 mb_groups details of multiblock allocator buddy cache of free blocks
1276..............................................................................
127712782.0 /proc/consoles
1279------------------
1280Shows registered system console lines.
12811282To see which character device lines are currently used for the system console
1283/dev/console, you may simply look into the file /proc/consoles:
12841285 > cat /proc/consoles
1286 tty0 -WU (ECp) 4:7
1287 ttyS0 -W- (Ep) 4:64
12881289The columns are:
12901291 device name of the device
1292 operations R = can do read operations
1293 W = can do write operations
1294 U = can do unblank
1295 flags E = it is enabled
1296 C = it is preferred console
1297 B = it is primary boot console
1298 p = it is used for printk buffer
1299 b = it is not a TTY but a Braille device
1300 a = it is safe to use when cpu is offline
1301 major:minor major and minor number of the device separated by a colon
13021303------------------------------------------------------------------------------
1304Summary
1305------------------------------------------------------------------------------
1306The /proc file system serves information about the running system. It not only
1307allows access to process data but also allows you to request the kernel status
1308by reading files in the hierarchy.
13091310The directory structure of /proc reflects the types of information and makes
1311it easy, if not obvious, where to look for specific data.
1312------------------------------------------------------------------------------
13131314------------------------------------------------------------------------------
1315CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1316------------------------------------------------------------------------------
13171318------------------------------------------------------------------------------
1319In This Chapter
1320------------------------------------------------------------------------------
1321* Modifying kernel parameters by writing into files found in /proc/sys
1322* Exploring the files which modify certain parameters
1323* Review of the /proc/sys file tree
1324------------------------------------------------------------------------------
132513261327A very interesting part of /proc is the directory /proc/sys. This is not only
1328a source of information, it also allows you to change parameters within the
1329kernel. Be very careful when attempting this. You can optimize your system,
1330but you can also cause it to crash. Never alter kernel parameters on a
1331production system. Set up a development machine and test to make sure that
1332everything works the way you want it to. You may have no alternative but to
1333reboot the machine once an error has been made.
13341335To change a value, simply echo the new value into the file. An example is
1336given below in the section on the file system data. You need to be root to do
1337this. You can create your own boot script to perform this every time your
1338system boots.
13391340The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1341general things in the operation of the Linux kernel. Since some of the files
1342can inadvertently disrupt your system, it is advisable to read both
1343documentation and source before actually making adjustments. In any case, be
1344very careful when writing to any of these files. The entries in /proc may
1345change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1346review the kernel documentation in the directory /usr/src/linux/Documentation.
1347This chapter is heavily based on the documentation included in the pre 2.2
1348kernels, and became part of it in version 2.2.1 of the Linux kernel.
13491350Please see: Documentation/sysctl/ directory for descriptions of these
1351entries.
13521353------------------------------------------------------------------------------
1354Summary
1355------------------------------------------------------------------------------
1356Certain aspects of kernel behavior can be modified at runtime, without the
1357need to recompile the kernel, or even to reboot the system. The files in the
1358/proc/sys tree can not only be read, but also modified. You can use the echo
1359command to write value into these files, thereby changing the default settings
1360of the kernel.
1361------------------------------------------------------------------------------
13621363------------------------------------------------------------------------------
1364CHAPTER 3: PER-PROCESS PARAMETERS
1365------------------------------------------------------------------------------
136613673.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1368--------------------------------------------------------------------------------
13691370These file can be used to adjust the badness heuristic used to select which
1371process gets killed in out of memory conditions.
13721373The badness heuristic assigns a value to each candidate task ranging from 0
1374(never kill) to 1000 (always kill) to determine which process is targeted. The
1375units are roughly a proportion along that range of allowed memory the process
1376may allocate from based on an estimation of its current memory and swap use.
1377For example, if a task is using all allowed memory, its badness score will be
13781000. If it is using half of its allowed memory, its score will be 500.
13791380There is an additional factor included in the badness score: root
1381processes are given 3% extra memory over other tasks.
13821383The amount of "allowed" memory depends on the context in which the oom killer
1384was called. If it is due to the memory assigned to the allocating task's cpuset
1385being exhausted, the allowed memory represents the set of mems assigned to that
1386cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1387memory represents the set of mempolicy nodes. If it is due to a memory
1388limit (or swap limit) being reached, the allowed memory is that configured
1389limit. Finally, if it is due to the entire system being out of memory, the
1390allowed memory represents all allocatable resources.
13911392The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1393is used to determine which task to kill. Acceptable values range from -1000
1394(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1395polarize the preference for oom killing either by always preferring a certain
1396task or completely disabling it. The lowest possible value, -1000, is
1397equivalent to disabling oom killing entirely for that task since it will always
1398report a badness score of 0.
13991400Consequently, it is very simple for userspace to define the amount of memory to
1401consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1402example, is roughly equivalent to allowing the remainder of tasks sharing the
1403same system, cpuset, mempolicy, or memory controller resources to use at least
140450% more memory. A value of -500, on the other hand, would be roughly
1405equivalent to discounting 50% of the task's allowed memory from being considered
1406as scoring against the task.
14071408For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1409be used to tune the badness score. Its acceptable values range from -16
1410(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1411(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1412scaled linearly with /proc/<pid>/oom_score_adj.
14131414The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1415value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1416requires CAP_SYS_RESOURCE.
14171418Caveat: when a parent task is selected, the oom killer will sacrifice any first
1419generation children with separate address spaces instead, if possible. This
1420avoids servers and important system daemons from being killed and loses the
1421minimal amount of work.
1422142314243.2 /proc/<pid>/oom_score - Display current oom-killer score
1425-------------------------------------------------------------
14261427This file can be used to check the current score used by the oom-killer is for
1428any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1429process should be killed in an out-of-memory situation.
1430143114323.3 /proc/<pid>/io - Display the IO accounting fields
1433-------------------------------------------------------
14341435This file contains IO statistics for each running process
14361437Example
1438-------
14391440test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1441[1] 3828
14421443test:/tmp # cat /proc/3828/io
1444rchar: 323934931
1445wchar: 323929600
1446syscr: 632687
1447syscw: 632675
1448read_bytes: 0
1449write_bytes: 323932160
1450cancelled_write_bytes: 0
145114521453Description
1454-----------
14551456rchar
1457-----
14581459I/O counter: chars read
1460The number of bytes which this task has caused to be read from storage. This
1461is simply the sum of bytes which this process passed to read() and pread().
1462It includes things like tty IO and it is unaffected by whether or not actual
1463physical disk IO was required (the read might have been satisfied from
1464pagecache)
146514661467wchar
1468-----
14691470I/O counter: chars written
1471The number of bytes which this task has caused, or shall cause to be written
1472to disk. Similar caveats apply here as with rchar.
147314741475syscr
1476-----
14771478I/O counter: read syscalls
1479Attempt to count the number of read I/O operations, i.e. syscalls like read()
1480and pread().
148114821483syscw
1484-----
14851486I/O counter: write syscalls
1487Attempt to count the number of write I/O operations, i.e. syscalls like
1488write() and pwrite().
148914901491read_bytes
1492----------
14931494I/O counter: bytes read
1495Attempt to count the number of bytes which this process really did cause to
1496be fetched from the storage layer. Done at the submit_bio() level, so it is
1497accurate for block-backed filesystems. <please add status regarding NFS and
1498CIFS at a later time>
149915001501write_bytes
1502-----------
15031504I/O counter: bytes written
1505Attempt to count the number of bytes which this process caused to be sent to
1506the storage layer. This is done at page-dirtying time.
150715081509cancelled_write_bytes
1510---------------------
15111512The big inaccuracy here is truncate. If a process writes 1MB to a file and
1513then deletes the file, it will in fact perform no writeout. But it will have
1514been accounted as having caused 1MB of write.
1515In other words: The number of bytes which this process caused to not happen,
1516by truncating pagecache. A task can cause "negative" IO too. If this task
1517truncates some dirty pagecache, some IO which another task has been accounted
1518for (in its write_bytes) will not be happening. We _could_ just subtract that
1519from the truncating task's write_bytes, but there is information loss in doing
1520that.
152115221523Note
1524----
15251526At its current implementation state, this is a bit racy on 32-bit machines: if
1527process A reads process B's /proc/pid/io while process B is updating one of
1528those 64-bit counters, process A could see an intermediate result.
152915301531More information about this can be found within the taskstats documentation in
1532Documentation/accounting.
153315343.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1535---------------------------------------------------------------
1536When a process is dumped, all anonymous memory is written to a core file as
1537long as the size of the core file isn't limited. But sometimes we don't want
1538to dump some memory segments, for example, huge shared memory. Conversely,
1539sometimes we want to save file-backed memory segments into a core file, not
1540only the individual files.
15411542/proc/<pid>/coredump_filter allows you to customize which memory segments
1543will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1544of memory types. If a bit of the bitmask is set, memory segments of the
1545corresponding memory type are dumped, otherwise they are not dumped.
15461547The following 7 memory types are supported:
1548 - (bit 0) anonymous private memory
1549 - (bit 1) anonymous shared memory
1550 - (bit 2) file-backed private memory
1551 - (bit 3) file-backed shared memory
1552 - (bit 4) ELF header pages in file-backed private memory areas (it is
1553 effective only if the bit 2 is cleared)
1554 - (bit 5) hugetlb private memory
1555 - (bit 6) hugetlb shared memory
15561557 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1558 are always dumped regardless of the bitmask status.
15591560 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1561 effected by bit 5-6.
15621563Default value of coredump_filter is 0x23; this means all anonymous memory
1564segments and hugetlb private memory are dumped.
15651566If you don't want to dump all shared memory segments attached to pid 1234,
1567write 0x21 to the process's proc file.
15681569 $ echo 0x21 > /proc/1234/coredump_filter
15701571When a new process is created, the process inherits the bitmask status from its
1572parent. It is useful to set up coredump_filter before the program runs.
1573For example:
15741575 $ echo 0x7 > /proc/self/coredump_filter
1576 $ ./some_program
157715783.5 /proc/<pid>/mountinfo - Information about mounts
1579--------------------------------------------------------
15801581This file contains lines of the form:
1582158336 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1584(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
15851586(1) mount ID: unique identifier of the mount (may be reused after umount)
1587(2) parent ID: ID of parent (or of self for the top of the mount tree)
1588(3) major:minor: value of st_dev for files on filesystem
1589(4) root: root of the mount within the filesystem
1590(5) mount point: mount point relative to the process's root
1591(6) mount options: per mount options
1592(7) optional fields: zero or more fields of the form "tag[:value]"
1593(8) separator: marks the end of the optional fields
1594(9) filesystem type: name of filesystem of the form "type[.subtype]"
1595(10) mount source: filesystem specific information or "none"
1596(11) super options: per super block options
15971598Parsers should ignore all unrecognised optional fields. Currently the
1599possible optional fields are:
16001601shared:X mount is shared in peer group X
1602master:X mount is slave to peer group X
1603propagate_from:X mount is slave and receives propagation from peer group X (*)
1604unbindable mount is unbindable
16051606(*) X is the closest dominant peer group under the process's root. If
1607X is the immediate master of the mount, or if there's no dominant peer
1608group under the same root, then only the "master:X" field is present
1609and not the "propagate_from:X" field.
16101611For more information on mount propagation see:
16121613 Documentation/filesystems/sharedsubtree.txt
1614161516163.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1617--------------------------------------------------------
1618These files provide a method to access a tasks comm value. It also allows for
1619a task to set its own or one of its thread siblings comm value. The comm value
1620is limited in size compared to the cmdline value, so writing anything longer
1621then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1622comm value.
1623162416253.7 /proc/<pid>/task/<tid>/children - Information about task children
1626-------------------------------------------------------------------------
1627This file provides a fast way to retrieve first level children pids
1628of a task pointed by <pid>/<tid> pair. The format is a space separated
1629stream of pids.
16301631Note the "first level" here -- if a child has own children they will
1632not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1633to obtain the descendants.
16341635Since this interface is intended to be fast and cheap it doesn't
1636guarantee to provide precise results and some children might be
1637skipped, especially if they've exited right after we printed their
1638pids, so one need to either stop or freeze processes being inspected
1639if precise results are needed.
1640164116423.7 /proc/<pid>/fdinfo/<fd> - Information about opened file
1643---------------------------------------------------------------
1644This file provides information associated with an opened file. The regular
1645files have at least two fields -- 'pos' and 'flags'. The 'pos' represents
1646the current offset of the opened file in decimal form [see lseek(2) for
1647details] and 'flags' denotes the octal O_xxx mask the file has been
1648created with [see open(2) for details].
16491650A typical output is
16511652 pos: 0
1653 flags: 0100002
16541655The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1656pair provide additional information particular to the objects they represent.
16571658 Eventfd files
1659 ~~~~~~~~~~~~~
1660 pos: 0
1661 flags: 04002
1662 eventfd-count: 5a
16631664 where 'eventfd-count' is hex value of a counter.
16651666 Signalfd files
1667 ~~~~~~~~~~~~~~
1668 pos: 0
1669 flags: 04002
1670 sigmask: 0000000000000200
16711672 where 'sigmask' is hex value of the signal mask associated
1673 with a file.
16741675 Epoll files
1676 ~~~~~~~~~~~
1677 pos: 0
1678 flags: 02
1679 tfd: 5 events: 1d data: ffffffffffffffff
16801681 where 'tfd' is a target file descriptor number in decimal form,
1682 'events' is events mask being watched and the 'data' is data
1683 associated with a target [see epoll(7) for more details].
16841685 Fsnotify files
1686 ~~~~~~~~~~~~~~
1687 For inotify files the format is the following
16881689 pos: 0
1690 flags: 02000000
1691 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
16921693 where 'wd' is a watch descriptor in decimal form, ie a target file
1694 descriptor number, 'ino' and 'sdev' are inode and device where the
1695 target file resides and the 'mask' is the mask of events, all in hex
1696 form [see inotify(7) for more details].
16971698 If the kernel was built with exportfs support, the path to the target
1699 file is encoded as a file handle. The file handle is provided by three
1700 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1701 format.
17021703 If the kernel is built without exportfs support the file handle won't be
1704 printed out.
17051706 If there is no inotify mark attached yet the 'inotify' line will be omitted.
17071708 For fanotify files the format is
17091710 pos: 0
1711 flags: 02
1712 fanotify flags:10 event-flags:0
1713 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1714 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
17151716 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1717 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1718 flags associated with mark which are tracked separately from events
1719 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1720 mask and 'ignored_mask' is the mask of events which are to be ignored.
1721 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1722 does provide information about flags and mask used in fanotify_mark
1723 call [see fsnotify manpage for details].
17241725 While the first three lines are mandatory and always printed, the rest is
1726 optional and may be omitted if no marks created yet.
172717281729------------------------------------------------------------------------------
1730Configuring procfs
1731------------------------------------------------------------------------------
173217334.1 Mount options
1734---------------------
17351736The following mount options are supported:
17371738 hidepid= Set /proc/<pid>/ access mode.
1739 gid= Set the group authorized to learn processes information.
17401741hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1742(default).
17431744hidepid=1 means users may not access any /proc/<pid>/ directories but their
1745own. Sensitive files like cmdline, sched*, status are now protected against
1746other users. This makes it impossible to learn whether any user runs
1747specific program (given the program doesn't reveal itself by its behaviour).
1748As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1749poorly written programs passing sensitive information via program arguments are
1750now protected against local eavesdroppers.
17511752hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1753users. It doesn't mean that it hides a fact whether a process with a specific
1754pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1755but it hides process' uid and gid, which may be learned by stat()'ing
1756/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1757information about running processes, whether some daemon runs with elevated
1758privileges, whether other user runs some sensitive program, whether other users
1759run any program at all, etc.
17601761gid= defines a group authorized to learn processes information otherwise
1762prohibited by hidepid=. If you use some daemon like identd which needs to learn
1763information about processes information, just add identd to this group.
1764